Sensor chip, sensor cartridge, and analysis apparatus

ABSTRACT

A sensor chip includes: a substrate that has a planar portion; and a diffraction grating on the planar portion and having a metal surface, the diffraction grating having a target substance thereon and including: a plurality of first protrusions periodically arranged in a period equal to or greater than 100 nm and equal to or less than 1000 nm in a first direction parallel to the planar portion, a plurality of base portions located between two adjacent first protrusions and configures abase of the substrate, a plurality of second protrusions formed on upper faces of the plurality of first protrusions, and a plurality of third protrusions formed on the plurality of base portions.

CROSS REFERENCES TO RELATED APPLICATIONS

This is a continuation application of U.S. Ser. No. 12/947,888 filedNov. 17, 2010, which claims priority to Japanese Patent Application Nos.2009-281480 filed Dec. 11, 2009, 2009-263706 filed Nov. 19, 2009,2010-192838 filed Aug. 30, 2010, and 2010-192839 filed Aug. 30, 2010 allof which are incorporated herein by reference in their entireties.

BACKGROUND

1. Technical Field

The invention relates to a sensor chip, a sensor cartridge, and ananalysis apparatus.

2. Related Art

Recently, demand for sensors used in medical diagnoses, the inspectionof food, and the like has been increasing, and thus development ofsensor technology that implements a sensor that is miniaturized andcapable of sensing at high speed has been demanded. In order to respondto such demands, various types of sensors using electrochemicaltechniques and the like have been reviewed. Among these, from theviewpoint of easy integration, low cost, and low sensitivity to themeasurement environment, sensors using surface plasmon resonance (SPR)have drawn attention.

Here, the surface plasmon is an oscillation mode of an electron wavethat is coupled with light depending on boundary conditions specific tothe surface. As a method of exciting the surface plasmon, there is amethod in which a diffraction grating is imprinted on a metal surfaceand light and plasmon are coupled together or a method in which anevanescent wave is used. For example, as a configuration of a sensorthat uses SPR, a configuration in which a total reflection-type prismand a metal film brought into contact with a target substance that isformed on the surface of the prism are included is known. According tosuch a configuration, whether or not a target substance is adsorbed isdetected, including whether or not an antigen is adsorbed in anantigen-antibody reaction and the like.

However, while propagation-type surface plasmon exists on the metalsurface, localized-type surface plasmon exists in a metal fine particle.It is known that, when the localized-type surface plasmon, that is, thesurface plasmon that exists locally on the microstructure of the surfaceis excited, a markedly enhanced electric field is generated.

Thus, in order to improve the sensitivity of the sensor, a sensor thatuses a localized surface plasmon resonance (LSPR) using metal fineparticles or metal nanostructures is proposed. For example, inJP-A-2000-356587, by irradiating light onto a transparent substratehaving a surface to which metal fine particles are fixed in a film shapeand measuring the absorbance of light being transmitted through themetal fine particles, a change in the medium near the metal fineparticles is detected, whereby adsorption or deposition of a targetsubstance is detected.

However, according to JP-A-2000-356587, it is difficult to produce metalfine particles that have a uniform size (dimension or shape) and toregularly arrange the metal fine particles. When the size or thearrangement of the metal fine particles cannot be controlled, there arevariations in absorption due to resonance or a resonant wavelength.Accordingly, the width of the absorbance spectrum becomes broad, and thepeak intensity decreases. Accordingly, a change in the signal detectingthe change in the medium near the metal fine particles is low, and thereare limitations on improving the sensitivity of the sensor. Therefore,the sensitivity of the sensor is insufficient for use in specifying asubstance from the absorbance spectrum or the like.

SUMMARY

An advantage of some aspects of the invention is that it provides asensor chip, a sensor cartridge, and an analysis apparatus capable ofspecifying a target substance from a Raman spectroscopic spectrum byimproving the sensitivity of a sensor.

Aspects of the invention employ the following configurations.

According to a first aspect of the invention, there is provided a sensorchip including: a substrate that has a planar portion; and a diffractiongrating on the planar portion and having a metal surface, thediffraction having a target substance thereon and including: a pluralityof first protrusions periodically arranged in a period equal to orgreater than 100 nm and equal to or less than 1000 nm in a firstdirection that is parallel to the planar portion, a plurality of baseportions located between two adjacent first protrusions and configures abase of the substrate, a plurality of second protrusions on upper facesof the plurality of the first protrusions, and a plurality of thirdprotrusions on the plurality of base portions.

According to the first aspect of the invention, a proximal electricfield that is enhanced through surface plasmon resonance by the firstprotrusions is excited toward the surface having the same shape, andsurface enhanced Raman scattering (SERS) having a high degree ofenhancement can be further exhibited by a metallic microstructureaccording to the second protrusions and the third protrusions. Morespecifically, when light is incident to a surface on which a pluralityof the first protrusions, a plurality of the second protrusions, and aplurality of the third protrusions are formed, a surface-specificoscillation mode (surface plasmon) is formed by the plurality of thefirst protrusions. Then, free electrons are in a state of resonantoscillation accompanying the oscillation of light, and accordingly, theoscillation of an electromagnetic wave is excited accompanying theoscillation of the free electrons. Since the oscillation of the freeelectrons is influenced by the oscillation of this electromagnetic wave,a system acquired by coupling the oscillations of both parties, that is,a so-called surface plasmon polariton (SPP) is formed. Accordingly,localized surface plasmon resonance (LSPR) is excited near the pluralityof the second protrusions and the plurality of the third protrusions. Inthis structure, since the distance between two of the second protrusionsadjacent to each other and the distance between two of the thirdprotrusions adjacent to each other are short, an extremely strongenhanced electric field is generated near the contact points thereof.Then, when one to several target substances are adsorbed on the contactpoints, the SERS occurs from the contact points. Accordingly, a sharpSERS spectrum that is specific to the target substance can be acquired.Therefore, a sensor chip capable of specifying a target substance from aSERS spectrum by improving the sensitivity of the sensor can beprovided. By appropriately changing the period and the height of thefirst protrusion, the height of the second protrusion, and the height ofthe third protrusion, the position of the resonant peak can be adjustedto an arbitrary wavelength. Accordingly, it is possible to appropriatelyselect the wavelength of light that is emitted when specifying a targetsubstance, whereby the width of the measurement range increases.

In the above-described sensor chip, it is preferable that the pluralityof the first protrusions is periodically arranged in a second directionthat intersects with the first direction and is parallel to the planarportion. In such a case, sensing can be performed under conditions ofplasmon resonance that are broader than that of a case where the firstprotrusions are formed periodically only in the direction (the firstdirection) parallel to the planar portion of the substrate. Accordingly,a sensor chip capable of specifying a target substance from a SERSspectrum by improving the sensitivity of the sensor can be provided.Furthermore, in addition to the period of the first protrusions in thefirst direction, the period in the second direction can be appropriatelychanged. Accordingly, it is possible to appropriately select thewavelength of light that is emitted when specifying a target substance,whereby the width of the measurement range increases.

In the above-described sensor chip, it is preferable that the pluralityof second protrusions and the plurality of third protrusions areperiodically arranged in a third direction that is parallel to theplanar portion. In such a case, the periods of the second protrusionsand the third protrusions can be appropriately changed. Accordingly, itis possible to appropriately select the wavelength of light that isemitted when specifying a target substance, whereby the width of themeasurement range increases.

In the above-described sensor chip, it is preferable that the pluralityof second protrusions and the plurality of third protrusions areperiodically arranged in a fourth direction that intersects with thethird direction and is parallel to the planar portion. In such a case,sensing can be performed under conditions of plasmon resonance that arebroader than that of a case where the second protrusions and the thirdprotrusions are formed only in the direction (the third direction)parallel to the planar portion of the substrate. Accordingly, a sensorchip capable of specifying a target substance from a SERS spectrum byimproving the sensitivity of the sensor can be provided. Furthermore, inaddition to the periods of the second protrusions and the thirdprotrusions in the third direction, the period in the fourth directioncan be appropriately changed. Accordingly, it is possible toappropriately select the wavelength of light that is emitted whenspecifying a target substance, whereby the width of the measurementrange increases.

In the above-described sensor chip, it is preferable that the pluralityof second protrusions and the plurality of third protrusions are formedfrom fine particles. In such a case, a sensor chip capable of specifyinga target substance from a SERS spectrum by improving the sensitivity ofthe sensor can be provided.

In the above-described sensor chip, it is preferable that the metal thatcomposes the surface of the diffraction grating is gold or silver. Insuch a case, since gold or silver has characteristics for exhibiting theSPP, the LSPR, and the SERS, the SPP, the LSPR, and the SERS can beeasily exhibited, whereby a target substance can be detected with highsensitivity.

According to a second aspect of the invention, there is provided asensor cartridge including: the above-described sensor chip; a transportunit that transports the target substance to a surface of the sensorchip; a placement unit in which the sensor chip is placed; a casing thathouses the sensor chip, the transport unit, and the placement unit; andan irradiation window that is disposed at a position facing the surfaceof the sensor chip on the casing.

According to the second aspect of the invention, since theabove-described sensor chip is included, a target molecule can bedetected by performing selective spectroscopy for the Raman scatteringlight. Therefore, a sensor cartridge capable of specifying a targetsubstance from the SERS spectrum by improving the sensitivity of thesensor can be provided.

According to a third aspect of the invention, there is provided ananalysis apparatus including: the above-described sensor chip; a lightsource that emits light to the sensor chip; and a photo detector thatdetects light scattered by the sensor chip.

According to the third aspect of the invention, since theabove-described sensor chip is included, a target molecule can bedetected by performing selective spectroscopy for the Raman scatteringlight. Therefore, an analysis apparatus capable of specifying a targetsubstance from a SERS spectrum by improving the sensitivity of thesensor can be provided.

According to a fourth aspect of the invention, there is provided asensor chip including: a substrate that has a planar portion; and adiffraction grating having a composite pattern in the planar portion anda metal surface, the diffraction grating having a target substancethereon and superimposedly including: a first protrusion pattern inwhich a plurality of first protrusions is periodically arranged in aperiod equal to or greater than 100 nm and equal to or less than 1000nm, a second protrusion pattern in which a plurality of secondprotrusions is periodically arranged in the plurality of firstprotrusions in a period shorter than that of the first protrusionpattern and a third protrusion pattern in which a plurality of thirdprotrusions is arranged periodically in a period shorter than that ofthe first protrusion pattern in a base portion of the substrate locatedbetween two adjacent first protrusions.

According to the fourth aspect of the invention, a proximal electricfield that is enhanced through surface plasmon resonance by the firstprotrusion is excited toward the surface having the same shape, andsurface enhanced Raman scattering (SERS) having a high degree ofenhancement can be further exhibited by a metallic microstructure due tothe second protrusion. More specifically, when light is incident to aface on which the first protrusion pattern and the second protrusionpattern are formed, a surface-specific oscillation mode (surfaceplasmon) is formed by the first protrusion pattern. Then, free electronsare in a state of resonant oscillation accompanying the oscillation oflight, and accordingly, the oscillation of an electromagnetic wave isexcited accompanying the oscillation of the free electrons. Since theoscillation of the free electrons is influenced by the oscillation ofthis electromagnetic wave, a system acquired by coupling theoscillations of both the parties, that is, a so-called surface plasmonpolariton (SPP) is formed. Accordingly, localized surface plasmonresonance (LSPR) is excited near the second protrusion pattern. In thisstructure, since the distance between two of the second protrusionsadjacent to each other is short, an extremely strong enhanced electricfield is generated near the contact points thereof. Then, when one toseveral target substances are adsorbed on the contact points, the SERSoccurs from the contact points. Accordingly, a sharp SERS spectrum thatis specific to the target substance can be acquired. Therefore, a sensorchip capable of specifying a target substance from a SERS spectrum byimproving the sensitivity of the sensor can be provided. Byappropriately changing the period and the height of the firstprotrusion, the height of the second protrusion, and the height of thethird protrusion, the position of the resonant peak can be adjusted toan arbitrary wavelength. Accordingly, it is possible to appropriatelyselect the wavelength of light that is emitted when specifying a targetsubstance, whereby the width of the measurement range increases.

In the above-described sensor chip, it is preferable that the pluralityof first protrusions is periodically arranged in a first direction thatis parallel to the planar portion and is periodically arranged in asecond direction that intersects with the first direction and isparallel to the planar portion. In such a case, sensing can be performedunder conditions of plasmon resonance that are broader than that of acase where the first protrusions are formed periodically only in thedirection (the first direction) parallel to the planar portion of thesubstrate. Accordingly, a sensor chip capable of specifying a targetsubstance from a SERS spectrum by improving the sensitivity of thesensor can be provided. Furthermore, in addition to the period of thefirst protrusions in the first direction, the period in the seconddirection can be appropriately changed. Accordingly, it is possible toappropriately select the wavelength of light that is emitted whenspecifying a target substance, whereby the width of the measurementrange increases.

In the above-described sensor chip, it is preferable that the pluralityof second protrusions and the plurality of third protrusions areperiodically arranged in a third direction that is parallel to theplanar portion. In such a case, the periods of the second protrusionsand the third protrusions can be appropriately changed. Accordingly, itis possible to appropriately select the wavelength of light that isemitted when specifying a target substance, whereby the width of themeasurement range increases.

In the above-described sensor chip, it is preferable that the pluralityof second protrusions and the plurality of third protrusions areperiodically arranged in a fourth direction that intersects with thethird direction and is parallel to the planar portion. In such a case,sensing can be performed under conditions of plasmon resonance that arebroader than that of a case where the second protrusions and the thirdprotrusions are formed only in the direction (the third direction)parallel to the planar portion of the substrate. Accordingly, a sensorchip capable of specifying a target substance from a SERS spectrum byimproving the sensitivity of the sensor can be provided. Furthermore, inaddition to the periods of the second protrusions and the thirdprotrusions in the third direction, the period in the fourth directioncan be appropriately changed. Accordingly, it is possible toappropriately select the wavelength of light that is emitted whenspecifying a target substance, whereby the width of the measurementrange increases.

In the above-described sensor chip, it is preferable that the pluralityof second protrusions and the plurality of third protrusions are formedfrom fine particles. In such a case, a sensor chip capable of specifyinga target substance from a SERS spectrum by improving the sensitivity ofthe sensor can be provided.

In the above-described sensor chip, it is preferable that the metal thatcomposes the surface of the diffraction grating is gold or silver. Insuch a case, since gold or silver has a characteristic of exhibiting theSPP, the LSPR, and the SERS, the SPP, the LSPR, and the SERS can beeasily exhibited, whereby a target substance can be detected with highsensitivity.

According to a fifth aspect of the invention, there is provided a sensorcartridge including: the above-described sensor chip; a transport unitthat transports the target substance to a surface of the sensor chip; aplacement unit in which the sensor chip is placed; a casing that housesthe sensor chip, the transport unit, and the placement unit; and anirradiation window that is disposed at a position facing the surface ofthe sensor chip on the casing.

According to the fifth aspect of the invention, since theabove-described sensor chip is included, a target molecule can bedetected by performing selective spectroscopy for the Raman scatteringlight. Therefore, a sensor cartridge capable of specifying a targetsubstance from the SERS spectrum by improving the sensitivity of thesensor can be provided.

According to a sixth aspect of the invention, there is provided ananalysis apparatus including: the above-described sensor chip; a lightsource that emits light onto the sensor chip; and a photo detector thatdetects light scattered by the sensor chip.

According to the sixth aspect of the invention, since theabove-described sensor chip is included, a target molecule can bedetected by performing selective spectroscopy for the Raman scatteringlight. Therefore, an analysis apparatus capable of specifying a targetsubstance from a SERS spectrum by improving the sensitivity of thesensor can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIGS. 1A and 1B are schematic diagrams representing a schematicconfiguration of a sensor chip according to an embodiment of theinvention.

FIGS. 2A and 2B are diagrams representing a Raman scatteringspectroscopy.

FIGS. 3A and 3B are diagrams representing an electric field enhancingmechanism using LSPR.

FIG. 4 is a diagram representing the SERS spectroscopy.

FIG. 5 is a graph representing the intensity of reflected lightreflected from a single body of the first protrusion.

FIG. 6 is a graph representing the dispersion curve of SPP.

FIG. 7 is a graph representing the intensity of reflected light of asensor chip according to an embodiment of the invention.

FIG. 8 is a schematic diagram of a sensor chip in which a plurality ofthe second protrusions is formed on the planar portion of the substrate.

FIG. 9 is a graph representing the intensity of reflected light of asensor chip shown in FIG. 8.

FIGS. 10A to 10F are diagrams representing the manufacturing process ofthe sensor chip.

FIG. 11 is a schematic configuration diagram of a modified example of asensor chip having the first protrusions.

FIGS. 12A and 12B are schematic configuration diagrams showing modifiedexamples of a sensor chip having the second protrusions.

FIGS. 13A and 13B are schematic configuration diagrams showing modifiedexamples of a sensor chip having the second protrusions.

FIG. 14 is a schematic diagram representing an example of an analysisapparatus.

FIG. 15 is a schematic diagram showing a schematic configuration of asensor chip according to an embodiment of the invention.

FIG. 16 is a schematic diagram showing a schematic configuration of asensor chip according to an embodiment of the invention.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, an embodiment of the invention will be described withreference to the accompanying drawings. Such an embodiment representsone aspect of the invention and is not for the purpose of limiting theinvention. Thus, various changes can be arbitrarily made therein withinthe scope of the technical idea of the invention. In the drawingsdescribed below, for easy understanding of each configuration, thescales, the numbers, and the like of structures are different from thoseof the actual structures.

FIGS. 1A and 1B are schematic diagrams representing a schematicconfiguration of a sensor chip according to an embodiment of theinvention. FIG. 1A is a perspective view of the sensor chip showing aschematic configuration thereof. FIG. 1B is a cross-sectional view ofthe sensor chip showing a schematic configuration thereof. In FIG. 1B,the reference sign P1 is a period of the first protrusion (the firstconvex shape), the reference sign P2 is a period of the secondprotrusion (the second convex shape) and the third protrusion (thirdconvex shape), the reference sign T1 is the height of the firstprotrusion (the depth of the groove), the reference sign T2 is theheight of the second protrusion (the depth of the groove), the referencesign T3 is the height of the third protrusion (the depth of the groove),the reference sign W1 represents the width of the first protrusion, andthe reference sign W2 is the distance between two of the firstprotrusions that are adjacent to each other.

FIGS. 15 and 16 are schematic diagrams showing schematic configurationsof sensor chips according to an embodiment of the invention, whichcorrespond to FIG. 1B. In FIGS. 15 and 16, the reference sign P1 is aperiod of the first protrusion (the first convex shape), the referencesign P2 is a period of the second protrusion (the second convex shape)and the third protrusion (the third convex shape), the reference sign T1is the height of the first protrusion (the depth of the groove), thereference sign T2 is the height of the second protrusion (the depth ofthe groove), the reference sign T3 is the height of the third protrusion(the depth of the groove), the reference sign W1 represents the width ofthe first protrusion, and the reference sign W2 is the distance betweentwo of the first protrusions that are adjacent to each other.

The sensor chip 1 is used for placing a target substance in adiffraction grating 9 that is formed in a substrate 10 containing metaland detecting the target substance by using localized surface Plasmonresonance (LSPR) and surface enhanced Raman scattering (SERS).

The diffraction grating 9 includes: a plurality of the first protrusions11 that is arranged in a period P1 equal to or greater than 100 nm andequal to or less than 1000 nm in the first direction that is parallel toa planar portion of the substrate 10; a plurality of base portions 10 athat is positioned between two of the first protrusions 11 adjacent toeach other and configures the base of the substrate 10; a plurality ofthe second protrusions 12 that is formed on an upper face 11 a of eachof the plurality of the first protrusions 11; and a plurality of thethird protrusions 13 that is formed on each of the plurality of the baseportions 10 a. The diffraction grating 9 has a surface formed from ametal and is formed on a planar portion 10 s of the substrate 10.

In other words, the diffraction grating 9 has a composite patternacquired by superimposing the first protrusion pattern in which aplurality of the first protrusions (the first convex shapes) 11 isarranged in a period P1 equal to or greater than 100 nm and equal to orless than 1000 nm in a direction perpendicular to the planar portion ofthe substrate 10, the second protrusion pattern in which a plurality ofthe second protrusions (the second convex shapes) 12 is arrangedperiodically in a period P2 shorter than that of the first protrusionpattern in each of the plurality of the first protrusions 11, and thethird protrusion pattern in which a plurality of the third protrusionsis arranged in a period P2 shorter than that of the first protrusionpattern in the base portion located between two of the first protrusions11 adjacent to each other, and has a surface formed from a metal. Andthe protrusions could also have a rounded/convex shape rather than therectangular shape shown in the drawings.

The “diffraction grating” described here represents a structure in whicha plurality of protrusion patterns (a plurality of protrusions) isperiodically arranged.

In addition, the “planar portion” described here represents an upperface portion of the substrate. In other words, the “planar portion”represents one surface portion of the substrate on which a targetsubstance is placed. The composite pattern that is formed bysuperimposing the first protrusion pattern, the second protrusionpattern, and the third protrusion pattern together is formed on at leastthe upper face portion of the substrate. The shape of the other surfaceportion, that is, a lower face portion of the substrate is notparticularly limited. However, in consideration of the processingprocess or the like performed for the planar portion (the upper faceportion) of the substrate, it is preferable that the lower face portionof the substrate is parallel to the base portion of the planar portionand is a flat face.

As an example of the configuration of the diffraction grating 9, asshown in FIG. 1B, there is a structure in which the substrate 10, thefirst protrusion 11, and the second protrusion 12 are all formed frommetal. In addition, as shown in FIG. 15, there is a structure in whichthe substrate 10 and the first protrusion 11 are formed by an insulatingmember formed from glass, resin, or the like, all the exposed portionsof the insulating member are covered with a metal film, and the secondprotrusion 12 formed from a metal is formed on the metal film, and thethird protrusion 13 formed from a metal is formed. In addition, as shownin FIG. 16, there is a structure in which all the substrate 10, thefirst protrusion 11, the second protrusion 12, and the third protrusion13 are formed by an insulating member, and all the exposed portions ofthe insulating member are covered with a metal film. In other words, thediffraction grating 9 has a configuration in which the base portion 10 aof the substrate 10 and at least the surfaces of the first protrusion11, the second protrusion 12, and the third protrusion 13 are formedfrom a metal.

The substrate 10, for example, has a structure in which a metal filmhaving a thickness of 150 nm or more is formed on a glass substrate.This metal film becomes the first protrusion 11, the second protrusion12, and the third protrusion 13 through a manufacturing process to bedescribed later. In this embodiment, as the substrate 10, a substrate inwhich a metal film is formed on the glass substrate is used. However,the substrate 10 is not limited thereto. For example, a substrate inwhich a metal film is formed on a quartz substrate or sapphire substratemay be used as the substrate 10. In addition, a flat plate formed frommetal may be used as the substrate.

The first protrusions 11 are formed on the planar portion 10 s of thesubstrate 10 so as to have a predetermined height T1. These firstprotrusions 11 are arranged in a period P1 that is shorter than thewavelength of light in a direction (the first direction) parallel to theplanar portion 10 s of the substrate 10. In the period P1, the width ofa single body of the first protrusion 11 in the first direction (thehorizontal direction in FIG. 1B) and the distance between two of thefirst protrusions 11 that are adjacent to each other are added together.In addition, the first protrusion 11 is in a rectangular convex shape inthe cross-sectional view, and a plurality of the first protrusions 11 isformed in a line and space (a stripe shape) in the plan view.

It is preferable that, for example, the period P1 of the firstprotrusions 11 is set in the range of 100 nm to 1000 nm, and the heightT1 of the first protrusions 11 is set in the range of 10 nm to 100 nm.Accordingly, the first protrusions 11 can serve as a structure forexhibiting the LSPR.

The width W1 of the first protrusion 11 in the first direction isgreater than the distance W2 between two of the first protrusions 11that are adjacent to each other (W1>W2). Accordingly, the spatialfilling rate of the first protrusions 11 in which the LSPR is excitedincreases.

Two or more second protrusions 12 are formed on the upper face 11 a ofeach of the plurality of the first protrusions 11 so as to have apredetermined height T2. In addition, two or more third protrusions 13are formed on each of the plurality of the base portions 10 a so as tohave a predetermined height T3.

The second protrusions 12 and the third protrusions 13 are arranged in aperiod P2 that is shorter than the wavelength of light in a direction(the third direction) parallel to the planar portion 10 s of thesubstrate 10. In the period P2, the width of a single body of the secondprotrusion 12 in the third direction (the horizontal direction in FIG.1B) and the distance between two of the second protrusions 12 that areadjacent to each other are added together (the width of the single bodyof the third protrusion 13 in the third direction and the distancebetween two of the third protrusions 13 adjacent to each other are addedtogether). Accordingly, the period P2 of the second protrusions 12 (thethird protrusion 13) is sufficiently shorter than that P1 of the firstprotrusions 11.

It is preferable that, for example, the period P2 of the secondprotrusions 12 and the third protrusions 13 is set to a value less than500 nm, and the heights T2 and T3 of the second and third protrusions 12and 13 are set to a value less than 200 nm. Accordingly, the secondprotrusions 12 and the third protrusions 13 can serve as a structure forexhibiting the SERS.

In this embodiment, the arrangement direction (the first direction) ofthe first protrusions 11 and the arrangement direction (the thirddirection) of the second protrusions 12 and the third protrusions 13 arethe same. In addition, second protrusion 12 and the third protrusion 13are in a rectangular convex shape in the cross-sectional view, and aplurality of the second protrusions 12 and a plurality of the thirdprotrusions 13 are formed in a line and space (a stripe shape) in theplan view.

As metal of the surface of the diffraction grating 9, for example, gold(Au), silver (Ag), copper (Cu), aluminum (Al), or an alloy thereof isused. In this embodiment, Au or Ag that has a characteristic ofexhibiting the SPP, the LSPR, and the SERS is used. Accordingly, theSPP, the LSPR, and the SERS can be easily exhibited, and a targetsubstance can be detected with high sensitivity.

Here, the LSPR, and the SERS will be described. When light is incidentto the surface of the sensor chip 1, that is, the face on which theplurality of the first protrusions 11, the plurality of the secondprotrusions 12, and the plurality of the third protrusions 13 areformed, a surface-specific oscillation mode (surface plasmon) is formedby the plurality of the first protrusions 11. However, the polarizingdirection of the incident light is perpendicular to the groove directionof the first protrusions 11. Then, the oscillation of an electromagneticwave is excited accompanied by the oscillation of free electrons. Sincethe oscillation of the free electrons is influenced by this oscillationof the electromagnetic wave, a system acquired by coupling both theoscillations, that is, a so-called surface plasmon polariton (SPP) isformed. In this embodiment, the incident angle of light is approximatelyvertical with respect to the surface of the sensor chip 1. However, theincident angle is not limited to this angle (vertical), as long as itsatisfies a condition for exciting the SPP.

This SPP propagates along the surface of the sensor chip 1, and morespecifically, along an interface between the air and the second andthird protrusions 12 and 13 and excites a strong localized electricfield near the second protrusion 12 and the third protrusion 13. Thecoupling of the SPP is sensitive to the wavelength of light, and thecoupling efficiency is high. As described above, localized surfaceplasmon resonance (LSPR) can be excited from the incident light that isin the air propagation mode through the SPP. Then, from the relationshipbetween the LSPR and Raman scattering light, surface enhanced Ramanscattering (SERS) can be used.

FIGS. 2A and 2B are diagrams representing a Raman scatteringspectroscopy. FIG. 2A represents the principle of the Raman scatteringspectroscopy. In addition, FIG. 2B represents a Raman spectrum (therelationship between a Raman shift and the intensity of Ramanscattering). In FIG. 2A, the reference sign L represents incident light(light of a single wavelength), the reference sign Ram represents Ramanscattering light, the reference sign Ray represents Rayleigh scatteringlight, and the reference sign X represents a target molecule (targetsubstance). In FIG. 2B, the horizontal axis represents the Raman shift.Here, the Raman shift is the difference between the frequency of theRaman scattering light Ram and the frequency of the incident light L andhas a value that is specific to the structure of the target molecule X.

As shown in FIG. 2A, when light L of a single wavelength is emitted tothe target molecule X, light having a wavelength different from that ofthe incident light is generated in the scattering light (Ramanscattering light Ram). The difference between the energy levels of theRaman scattering light Ram and the incident light L corresponds to theenergy of the oscillation level, the rotation level, or the electronlevels of the target molecule X. The target molecule X has anoscillation energy level that is specific to the structure thereof, andaccordingly, the target molecule X can be specified by using the light Lof a single wavelength.

For example, when the oscillation energy of the incident light L isdenoted by V1, the oscillation energy consumed by the target molecule Xis denoted by V2, and the oscillation energy of the Raman scatteringlight Ram is denoted by V3, V3=V1−V2. After colliding with the targetmolecule X, most of the incident light L has energy with the samemagnitude as that of energy before the collision. This elasticscattering light is termed Rayleigh scattering light Ray. For example,when the oscillation energy of the Rayleigh scattering light Ray isdenoted by V4, V4=V1.

From the Raman spectrum shown in FIG. 2B, it can be known that the Ramanscattering light Ram is weak by comparing the scattering intensity(spectrum peak) of the Raman scattering light Ram and the scatteringintensity of the Rayleigh scattering light Ray. As described above, theRaman scattering spectroscopy is a measurement technique that has asuperior capability for identifying a target molecule X and a lowsensitivity for sensing a target molecule X. Accordingly, in thisembodiment, in order to increase the sensitivity, spectroscopy using thesurface enhanced Raman scattering (SERS spectroscopy) is used (see FIG.4).

FIGS. 3A and 3B are diagrams representing an electric field enhancingmechanism using the LSPR. FIG. 3A is a schematic diagram representing astate when light is incident to a metal nanoparticle. FIG. 3B is adiagram representing an LSPR enhanced electric field. In FIG. 3A, thereference sign 100 represents a light source, the reference sign 101represents a metal nanoparticle, and the reference sign 102 representslight emitted from the light source. In FIG. 3B, the reference sign 103represents a surface localized electric field.

As shown in FIG. 3A, when the light 102 is incident to the metalnanoparticle 101, free electrons are in a state of resonant oscillationaccompanying the oscillation of the light 102. The particle diameter ofthe metal nanoparticle is smaller than the wavelength of the incidentlight. For example, the wavelength of the light is in the range of 400nm to 800 nm, and the particle diameter of the metal nanoparticle is inthe range of 10 nm to 100 nm. As the metal nanoparticle, Ag or Au isused.

Then, a strong surface localized electric field 103 is excited near themetal nanoparticle 101 accompanying the resonant oscillation of the freeelectrons (see FIG. 3B). As above, the LSPR can be excited by allowingthe light 102 to be incident to the metal nanoparticle 101.

FIG. 4 is a diagram representing the SERS spectroscopy. In FIG. 4, thereference sign 200 represents a substrate, the reference sign 201represents a metal nanostructure, the reference sign 202 represents aselective adsorption film, the reference sign 203 represents an enhancedelectric field, the reference sign 204 represents a target molecule, thereference sign 211 represents an incident laser beam, the reference sign212 represents Raman scattering light, and the reference sign 213represents Rayleigh scattering light. The selective adsorption film 202adsorbs the target molecule 204.

As shown in FIG. 4, when the laser beam 211 is incident to the metalnanostructure 201, free electrons are in a state of resonant oscillationaccompanying the oscillation of the laser beam 211. The size of themetal nanostructure 201 is smaller than the wavelength of the incidentlaser beam. Then, accompanying the resonant oscillation of the freeelectrons, a strong surface localized electric field is excited near themetal nanostructure 201. Accordingly, the LSPR is excited. When thedistance between the metal nanostructures 201 that are adjacent to eachother decreases, an extremely strong enhanced electric field 203 isgenerated near the contact point. When one to several target molecules204 are adsorbed on the contact points, the SERS occurs from the contactpoints. This point is also checked by the result of an enhanced electricfield generated between two adjacent silver nanoparticles that iscalculated by using a finite difference time domain (FDTD) method.Accordingly, by performing selective spectroscopy for the Ramanscattering light, the target molecule can be detected with highsensitivity.

This embodiment, as described above, has a structure in which the LSPRis excited by arranging the first protrusions 11 in the period P1shorter than the wavelength of the light in the direction parallel tothe planar portion of the substrate 10. In addition, this embodiment hasa structure in which the SERS is exhibited by forming two or more of thesecond protrusions 12 on the upper face 11 a of the first protrusion 11and forming two or more of the third protrusions 13 on the base portion10 a. More specifically, when light of a single wavelength is emitted toa target molecule, based on the principle of generating the Ramanscattering light, an enhanced magnetic field is generated near thecontact point by disposing the target molecules between two of thesecond protrusions 12 (the third protrusions 13) that are adjacent toeach other, whereby the SERS occurs. Accordingly, it is possible to usethe SERS spectroscopy capable of detecting a target substance withsensitivity that is higher than that of the Raman scatteringspectroscopy.

FIG. 5 is a graph representing the intensity of reflected lightreflected from a single body of the first protrusion. In FIG. 5, thehorizontal axis represents the wavelength of light, and the verticalaxis represents the intensity of the reflected light. The height T1 ofthe first protrusion 11 is taken as a parameter (T1=20 nm, 30 nm, and 40nm). In addition, in the structure of the sensor chip 1 according tothis embodiment, a value calculated by subtracting the intensity of thereflected light from the intensity of the incident light (assumed to be1.0) is absorbance.

The light is incident vertically to the first protrusion 11. Regardingthe polarization directions of the light, there are polarized lighthaving an electric field component parallel to the groove (the extendingdirection of an area between the first protrusions 11 adjacent to eachother) and TM (Transverse Magnetic) polarized light having an electricfield component perpendicular thereto. The period of the firstprotrusions 11 is 580 nm, and the resonant peak of the intensity of thereflected light is near a wavelength 630 nm. This resonant peakoriginates from the SPP, and as the height T1 of the first protrusion 11is increased, the resonant peak is shifted to the long wavelength side(the long wavelength region). When the height T1 of the first protrusion11 is 30 nm, the intensity of the reflected light is the highest, andaccordingly, it can be known that absorption is represented to be thestrongest.

FIG. 6 is a graph representing the dispersion curve of the SPP. In FIG.6, the reference sign C1 represents a dispersion curve (as an example,it represents a value at the interface of the air and Au) of the SPP,and the reference sign C2 represents a light line. The period of thefirst protrusion 11 is 580 nm. The position of the lattice vector of thefirst protrusion 11 is shown on the horizontal axis (corresponding to2π/P on the horizontal axis shown in FIG. 6). When a line extends fromthis position toward the upper side, the line intersects with thedispersion curve of the SPP. The wavelength corresponding to thisintersection is acquired by using the following equation.

λ=P1√[(E1·E2)/(E1+E2)]  (1)

In Equation (1), P1 represents the period of the first protrusions 11,E1 represents the complex permittivity of the air, and E2 represents thecomplex permittivity of Au. By substituting P1, E1, and E2 withrespective values in Equation (1), λ=620 nm is acquired (correspondingto w0 on the vertical axis shown in FIG. 6).

As the height T1 of the first protrusion 11 is increased, the imaginarypart of the wave number of the SPP increases. Accordingly, the real partof the wave number of the SPP decreases, whereby the intersection of theline extended from the position of the lattice vector and the dispersioncurve of the SPP moves from the upper right side to the lower left side.In other words, the resonant peak is shifted to the long wavelengthside.

FIG. 7 is a graph representing the intensity of reflected light of astructure in which the first protrusion 11 and the second protrusion 12(the third protrusion 13) are superimposed with each other, that is, thesensor chip 1 according to the embodiment of the invention. In FIG. 7,the horizontal axis represents the wavelength of light, and the verticalaxis represents the intensity of the reflected light. The height T2 ofthe second protrusion 12 (the height T3 of the third protrusion 13) istaken as a parameter (T2 (T3)=0 nm, 40 nm, and 80 nm). In addition, thegraph of the parameter T2=0 in this figure is the same as the graph ofthe parameter T1=30 shown in FIG. 5.

The light is incident vertically to the first protrusion 11. The heightT1 of the first protrusion 11 is 30 nm. In addition, the period P2 ofthe second protrusion 12 (the third protrusion 13) is 97 nm. Theresonant peak of the intensity of the reflected light is near awavelength 730 nm. Compared to the spectrum represented inJP-A-2000-356587, the width of the resonant peak is narrowed andsharpened. This resonant peak originates from the above-described SPP,and by superimposing the second protrusion 12 (the third protrusion 13)on the first protrusion 11, the position of the resonant peak is shiftedto the long wavelength side. At this time, the sharpness and thegradient of the resonant peak are maintained. In a case where the heightT2 (the height of the third protrusion 13) of the second protrusion 12is 40 nm, a strong localized electric field can be excited near thesurface of the second protrusion 12 by emitting light having awavelength of 730 nm. In addition, by appropriately changing the periodsP1 and P2 and the heights T1 and T2 (T3) of the first protrusion 11 andthe second protrusion 12 (the third protrusion 13), the position of theresonant peak can be adjusted to an arbitrary wavelength.

FIG. 8 is a diagram schematically showing the sensor chip 2 in a casewhere the first protrusion 11 is not formed in the planar portion 10 sof the substrate 10, and only the second protrusions 12 (the thirdprotrusions 13) are formed on the planar portion 10 s of the substrate10, that is, a case where a plurality of the second protrusions 12 (thethird protrusions 13) is formed on the planar portion 10 s of thesubstrate 10.

FIG. 9 is a graph representing the intensity of reflected light of asensor chip 2 in a case where a plurality of the second protrusions 12(the third protrusions 13) is formed on the planar portion 10 s of thesubstrate 10. In FIG. 9, the horizontal axis represents the wavelengthof light, and the vertical axis represents the intensity of thereflected light. The height T2 of the second protrusion 12 (the heightT3 of the third protrusion 13) is taken as a parameter (T2 (T3)=0 nm, 40nm, and 80 nm). The TM polarized light is incident vertically to thesecond protrusion 12 (the third protrusion 13). By referring to figure,a deep resonant peak of the intensity of the reflected light is notrecognized. From this result, it can be known that light energy canhardly be coupled with the second protrusion 12 (the third protrusion13) in a case where there is no first protrusion 11, that is, notthrough the SPP.

FIGS. 10A to 10F are diagrams representing the manufacturing process ofthe sensor chip. First, an Au film 31 is formed on a glass substrate 30by using a method such as a deposition method or a sputtering method.Next, the upper face of the Au film 31 is coated with a resist 32 byusing a method such as a spin coat method (see FIG. 10A). At this time,the Au film 31 is formed so as to have a film thickness Ta thick enoughto not transmit incident light (for example, 100 nm).

Next, a resist pattern 32 a is formed in a period Pa of 580 nm by usinga method such as an imprint method (see FIG. 10B). Next, the Au film 31is etched to a predetermined depth D1 (for example, 30 nm) by performingdry etching by using the resist pattern 32 a as a mask. Thereafter, byremoving the resist pattern 32 a, the first protrusion 31 a is formed(see FIG. 10C).

Next, the upper face of the Au film 31 on which the first protrusion 31a is formed is coated with a resist 33 by using a method such as a spincoat method (see FIG. 10D). Next, resist patterns 33 a is formed in aperiod Pb of 97 nm by using a method such as an imprint method (see FIG.10E). Next, the Au film 31 on which the first protrusion 31 a is formedby dry etching is etched to a predetermined depth D2 (for example, 40nm) by using the resist patterns 33 a as a mask. Thereafter, the secondprotrusion 31 b and the third protrusion 31 c are formed by removing theresist patterns 33 a (see FIG. 10F). By performing the above-describedprocesses, a sensor chip 3 according to an embodiment of the inventioncan be manufactured.

In the sensor chip 1 according to the embodiment of the invention, theLSPR is excited through the SPP by a metallic microstructure due to thefirst protrusion 11, and the SERS can be further exhibited by a metallicmicrostructure due to the second protrusion 12 and the third protrusion13. More specifically, when light is incident to a face on which aplurality of the first protrusions 11, a plurality of the secondprotrusions 12, and a plurality of the third protrusions 13 are formed,a surface-specific oscillation mode (surface plasmon) is formed by theplurality of the first protrusions 11. Then, free electrons are in astate of resonant oscillation due to oscillation of the light so as toexcite the SPP, whereby a strong surface localized electric field isexcited near the second protrusion 12 and the third protrusion 13.Accordingly, the LSPR is excited. In this structure, since the distancebetween two of the second protrusions 12 (the third protrusions 13)adjacent to each other is short, an extremely strong enhanced electricfield is generated near contact points. Then, when one to several targetsubstances are adsorbed on the contact points, the SERS occurs from thecontact points. Accordingly, intensity characteristics in which thespectrum width of the intensity of the reflected light is small and theresonant peak is sharp can be acquired, whereby the sensitivity of thesensor can be improved. Therefore, a sensor chip 1 capable of specifyinga target substance from the SERS spectrum by improving the sensitivityof the sensor can be provided. By appropriately changing the period P1and the height T1 of the first protrusion 11, the height T2 of thesecond protrusion 12, and the height T3 of the third protrusion 13, theposition of the resonant peak can be adjusted to an arbitrarywavelength. Accordingly, it is possible to appropriately select thewavelength of light that is emitted when specifying a target substance,whereby the width of the measurement range increases.

In addition, according to this configuration, since the secondprotrusions 12 and the third protrusions 13 are disposed periodically inthe third direction parallel to the planar portion of the substrate 10,the period P2 of the second protrusions 12 and the third protrusions 13can be appropriately changed. Accordingly, it is possible toappropriately select the wavelength of light that is emitted whenspecifying a target substance, whereby the width of the measurementrange increases.

In addition, according to this configuration, gold or silver is used asthe metal of the surface of the diffraction grating 9, and accordingly,the SPP, the LSPR and the SERS can be easily exhibited. Therefore, atarget substance can be detected with high sensitivity.

In addition, according to this configuration, the duty ratio of thefirst protrusion 11 satisfies the relationship of “W1>W2”, andaccordingly, the spatial filling rate of the first protrusion 11 inwhich the LSPR is excited increases. Therefore, sensing can be performedunder conditions of plasmon resonance that are broader than that of acase where the relationship of “W1<W2” is satisfied. In addition, theenergy of light emitted when specifying a target substance can beeffectively used.

In this embodiment, a structure in which the first protrusions 11 arearranged in the period P1 shorter than the wavelength of light in thedirection (the first direction) parallel to the planar portion of thesubstrate 10 is represented. However, the invention is not limitedthereto. A sensor chip 4 that has a structure of the first protrusionthat is different from that of the first protrusion 11 according to thisembodiment will be described with reference to FIG. 11.

FIG. 11 is a schematic perspective view showing the configuration of asensor chip 4 that has the first protrusions 41 in a form different fromthat of the above-described first protrusions 11. In this figure, forconvenience of description, the second protrusion and the thirdprotrusion are not shown.

As shown in FIG. 11, the first protrusion 41 is formed on the planarportion 40 s of a substrate 40. The first protrusions 41 are arranged ina period P3 shorter than the wavelength of the light in a direction (thefirst direction) parallel to the planar portion of the substrate 40. Inaddition, the first protrusions 41 are arranged in a period P4 that isshorter than the wavelength of the light in a second direction that isperpendicular to the first direction and is parallel to the planarportion of the substrate 40. Here, the second direction is not limitedto a direction that is perpendicular to the first direction and isparallel to the planar portion of the substrate 40 and may be adirection that intersects with the first direction and is parallel tothe planar portion of the substrate 40.

According to this structure, the SPP can be excited under conditions ofresonance that are broader than that of a case where the firstprotrusions are formed only in the direction (the first direction)parallel to the planar portion of the substrate 10. Accordingly, asensor chip 4 capable of specifying a target substance from the SERSspectrum by improving the sensitivity of the sensor can be provided.Furthermore, in addition to the period P3 of the first protrusions inthe first direction, the period P4 in the second direction can beappropriately changed. Accordingly, the wavelength of the light emittedwhen specifying a target substance can be appropriately selected,whereby the width of the measurement range increases.

In this embodiment, a structure in which the second protrusions 12 andthe third protrusions 13 are arranged in the period P2 shorter than thewavelength of the light in the direction (the third direction) parallelto the planar portion of the substrate 10, and more specifically, astructure in which the arrangement direction (the first direction) ofthe first protrusions 11 and the arrangement direction (the thirddirection) of the second protrusions 12 and the third protrusions 13 arethe same direction is represented. However, the invention is not limitedthereto. Thus, sensor chips 5, 6, 7, and 8 having a structure of thesecond protrusions and the third protrusions that is different from thatof the second protrusion 12 and the third protrusions 13 according tothis embodiment will be described with reference to FIGS. 12A to 13B.

FIGS. 12A and 12B are schematic perspective views showing theconfigurations of sensor chips having the second protrusion and thethird protrusion different from the above-described second protrusion 12and the third protrusion 13 in the form. FIG. 12A is a sensor chip 5that has the second protrusion 52 and the third protrusion 53. FIG. 12Bis a sensor chip 6 that has the second protrusion 62 and the thirdprotrusion 63.

As shown in FIG. 12A, two or more of the second protrusions 52 areformed on the upper face 51 a of each of a plurality of the firstprotrusions 51. Two or more of the third protrusions 53 are formed oneach of a plurality of the base portions 50 a. In the figure, as anexample, a structure in which the intersection angle of the arrangementdirection (the first direction) of the first protrusions 51 and thearrangement direction (the third direction) of the second protrusions 52and the third protrusions 53 is 45 degrees is represented.

As shown in FIG. 12B, two or more of the second protrusions 62 areformed on the upper face 61 a of each of the plurality of the firstprotrusions 61. Two or more of the third protrusion 63 are formed oneach of the plurality of the base portions 60 a. In the figure, as anexample, a structure in which the intersection angle of the arrangementdirection (the first direction) of the first protrusions 61 and thearrangement direction (the third direction) of the second protrusions 62and the third protrusions 63 is 90 degrees is represented.

According to this configuration, a sensor chip capable of specifying atarget substance from the SERS spectrum by improving the sensitivity ofthe sensor can be provided.

As shown in FIG. 13A, two or more of the second protrusions 72 areformed on the upper face 71 a of each of a plurality of the firstprotrusions (not shown). Two or more of the third protrusions 73 areformed on each of the plurality of the base portions 70 a. In addition,the second protrusions 72 and the third protrusions 73 are arrangedperiodically in the fourth direction that intersects with the thirddirection and is parallel to the planar portion of the substrate. Inthis figure, as an example, a structure in which the second protrusion72 and the third protrusion 73 have a circle shape in the plan view isrepresented. Alternatively, the second protrusions 72 and the thirdprotrusions 73 may be randomly disposed without having any periodicity.It is preferable that the interval of the second protrusions 72 and theinterval of the third protrusions 73 are set in the range of zero toseveral tens nm.

As shown in FIG. 13B, two or more of the second protrusions 82 areformed on the upper face 81 a of each of a plurality of the firstprotrusions (not shown). Two or more of the third protrusions 83 areformed on each of the plurality of the base portions 80 a. In addition,the second protrusions 82 and the third protrusions 83 are arrangedperiodically in the fourth direction that intersects with the thirddirection and is parallel to the planar portion of the substrate. Inthis figure, as an example, a structure in which the second protrusion82 and the third protrusion 83 have an oval shape in the plan view isrepresented. Alternatively, the second protrusions 82 and the thirdprotrusions 83 may be randomly disposed without having any periodicity.It is preferable that the interval of the second protrusions 82 and theinterval of the third protrusions 83 are set in the range of zero toseveral tens of nm.

According to this configuration, the density in the space in which theenhanced electric filed is generated can be increased, compared to acase where the second protrusions and the third protrusions are formedonly in the direction (the third direction) parallel to the planarportion of the substrate. Accordingly, a sensor chip capable ofspecifying a target substance from the SERS spectrum by improving thesensitivity of the sensor can be provided. Furthermore, in addition tothe period of the second protrusions and the third protrusions in thethird direction, the period in the fourth direction can be appropriatelychanged. Accordingly, the wavelength of the light emitted whenspecifying a target substance can be appropriately selected, whereby thewidth of the measurement range increases.

In addition, in this embodiment, the second protrusions and the thirdprotrusions are formed by patterning the Au film formed on the upperface of the glass substrate. However, the invention is not limitedthereto. For example, the second protrusions and the third protrusionsmay be fine particles. According to such a configuration, a sensor chipcapable of specifying a target substance from the SERS spectrum byimproving the sensitivity of the sensor can be provided.

In addition, in this embodiment, as the metal contained in thesubstrate, the metal contained in the first protrusion, the metalcontained in the second protrusion, and the metal contained in the thirdprotrusion, the same metal (gold or silver) is employed. However, theinvention is not limited thereto. For example, different metals (gold,silver, copper, aluminum, or an alloy thereof) may be combined so as tobe used, as in a case where the metal contained in the substrate isgold, the metal contained in the first protrusion is silver, and themetal contained in the second protrusion (the third protrusion) is analloy of gold and silver or the like.

Analysis Apparatus

FIG. 14 is a schematic diagram representing an example of an analysisapparatus that includes a sensor chip according to an embodiment of theinvention. In addition, arrows shown in FIG. 14 represent the transportdirection of a target substance (not shown).

As shown in FIG. 14, the analysis apparatus 1000 includes a sensor chip1001, a light source 1002, a photo detector 1003, a collimator lens1004, a polarization control device 1005, a dichroic mirror 1006, anobjective lens 1007, an objective lens 1008, and a transport unit 1010.The light source 1002 and the photo detector 1003 are electricallyconnected to a control device (not shown) through respective wirings.

The light source 1002 generates a laser beam that excites the SPP, theLSPR, and the SERS. The laser beam emitted from the light source 1002becomes a parallel beam through the collimator lens 1004, passes throughthe polarization control device 1005, is guided in the direction of thesensor chip 1001 by the dichroic mirror 1006 so as to be collected tothe objective lens 1007, and is incident to the sensor chip 1001. Atthis time, on the surface (for example, a face on which a metalnanostructure or a detection substance selecting mechanism is formed) ofthe sensor chip 1001, a target substance (not shown) is placed. Inaddition, by controlling the driving of a fan (not shown), the targetsubstance is introduced into the inside of the transport unit 1010 froma loading entrance 1011 and is discharged from a discharge opening 1012to the outside of the transport unit 1010. The size of the metalnanostructure is smaller than the wavelength of the laser beam.

When the laser beam is incident to the metal nanostructure, freeelectrons are in a state of resonant oscillation accompanying theoscillation of the laser beam, and a strong surface localized electricfield is excited near the metal nanostructure, whereby the LSPR isexcited. Then, when the distance between the metal nanostructuresadjacent to each other is shortened, an extremely strong enhancedelectric field is generated near the contact point. When one to severaltarget substances are adsorbed on the contact point, the SERS occursfrom the contact point.

The light (Raman scattering light or Rayleigh scattering light)scattered by the sensor chip 1001 passes through the objective lens1007, is guided in the direction of the photo detector 1003 by thedichroic mirror 1006 so as to be collected to the objective lens 1007,and is incident to the photo detector 1003. Then, the light is resolvedin a spectrum by the photo detector 1003, whereby spectrum informationcan be acquired.

According to this configuration, since a sensor chip according to anembodiment of the invention is included, the target molecule can bedetected by performing selective spectroscopy for the Raman scatteringlight. Therefore, an analysis apparatus 1000 capable of specifying atarget substance from the SERS spectrum by improving the sensitivity ofthe sensor can be provided.

The analysis apparatus 1000 includes a sensor cartridge 1100. The sensorcartridge 1100 includes the sensor chip 1001, the transport unit 1010that transports a target substance to the surface of the sensor chip1001, a placement unit 1101 in which the sensor chip 1001 is placed, anda casing 1110 that houses the above-described units. In a position ofthe casing 1110 that faces the sensor chip 1001, an irradiation window1111 is disposed. The laser beam emitted from the light source 1002passes through the irradiation window 1111 and is emitted to the surfaceof the sensor chip 1001. The sensor cartridge 1100 is located in theupper portion of the analysis apparatus 1000 and is detachably attachedto the main unit of the analysis apparatus 1000.

According to this configuration, since the above-described sensor chipaccording to an embodiment of the invention is included, the targetmolecule can be detected by performing selective spectroscopy for theRaman scattering light. Therefore, a sensor cartridge 1100 capable ofspecifying a target substance from the SERS spectrum by improving thesensitivity of the sensor can be provided.

The analysis apparatus according to an embodiment of the invention canbe broadly applied to detection of drugs or an explosive substances,medical treatments or physical examinations, and as a sensing apparatusused for inspection of foodstuffs. In addition, the analysis apparatuscan be used as an affinity sensor or the like that detects whether ornot a substance is adsorbed, including whether or not an antigen isadsorbed in an antigen-antibody reaction.

What is claimed is:
 1. An analysis apparatus comprising: a sensor chipwherein a substrate that has a planar portion, and a diffraction gratingthat includes a plurality of first protrusions periodically arranged ina period equal to or greater than 100 nm and equal to or less than 1000nm in a first direction that is parallel to the planar portion, aplurality of base portions that is located between two of the firstprotrusions adjacent to each other and configures a base of thesubstrate, a plurality of second protrusions that is formed on upperfaces of the plurality of the first protrusions, and a plurality ofthird protrusions that is formed on the plurality of base portions, hasa surface formed from a metal, and is formed on the planar portion; anda light source that emits light to the sensor chip wherein a wavelengthof the light is longer than the period of the second protrusions and thethird protrusions; and a photo detector that detects light acquired bythe sensor chip.
 2. The analysis apparatus sensor chip according toclaim 1, wherein the plurality of the first protrusions is periodicallyarranged in a second direction that intersects with the first directionand is parallel to the planar portion.
 3. The analysis apparatusaccording to claim 1, wherein the plurality of second protrusions andthe plurality of third protrusions are periodically arranged in a thirddirection that is parallel to the planar portion.
 4. The analysisapparatus to claim 3, wherein the plurality of second protrusions andthe plurality of third protrusions are periodically arranged in a fourthdirection that intersects with the third direction and is parallel tothe planar portion.
 5. The analysis apparatus to claim 1, wherein theplurality of second protrusions and the plurality of third protrusionsare formed from micro-particles.
 6. The analysis apparatus according toclaim 1, wherein the metal that composes the surface of the diffractiongrating is gold or silver.
 7. The analysis apparatus according to claim1, wherein a transport unit include a fan between entrance and adischarge opening, and a placement unit in which the sensor chip isplaced, and a casing that houses the sensor chip, the transport unit,and the placement unit, and an irradiation window that is disposed at aposition facing the surface of the sensor chip on the casing.
 8. Theanalysis apparatus according to claim 1, wherein the light sourcegenerates a laser beam that excites Surface Plasmon Polariton, LocalizedSurface Plasmon Resonance, and a Surface Enhanced Raman Scattering. 9.The analysis apparatus comprising: a sensor chip wherein a substratethat has a planar portion, and a diffraction grating, in which a targetsubstance is placed, that has a composite pattern that is formed in theplanar portion by superimposing a first concave-convex shape in which aplurality of first convex shapes is periodically arranged in a periodequal to or greater than 100 nm and equal to or less than 1000 nm, asecond concave-convex shape in which a plurality of second convex shapesis periodically arranged in the plurality of first convex shapes in aperiod shorter than that of the first concave-convex shape, and a thirdconcave-convex shapes in which a plurality of third convex shapes isarranged periodically in a period shorter than that of the firstconcave-convex shape in a base portion located between two of the firstconvex shapes adjacent to each other, and has a surface formed from ametal; and a light source that emits light to the sensor chip wherein awavelength of the light is longer than the period of the second convexshapes and the third convex shapes; and a photo detector that detectslight acquired by the sensor chip.
 10. The analysis apparatus accordingto claim 9, wherein the plurality of first convex shapes is periodicallyarranged in a first direction that is parallel to the planar portion andis periodically arranged in a second direction that intersects with thefirst direction and is parallel to the planar portion.
 11. The analysisapparatus according to claim 9, wherein the plurality of second convexshapes and the plurality of third convex shapes are periodicallyarranged in a third direction that is parallel to the planar portion.12. The analysis apparatus according to claim 11, wherein the pluralityof second convex shapes and the plurality of third convex shapes areperiodically arranged in a fourth direction that intersects with thethird direction and is parallel to the planar portion.
 13. The analysisapparatus according to claim 9, wherein the plurality of second convexshapes and the plurality of third convex shapes are formed frommicro-particles.
 14. The analysis apparatus according to claim 9,wherein the metal that composes the surface of the diffraction gratingis gold or silver.
 15. The analysis apparatus according to claim 9,wherein a transport unit include a fan between entrance and a dischargeopening, and a placement unit in which the sensor chip is placed, and acasing that houses the sensor chip, the transport unit, and theplacement unit, and an irradiation window that is disposed at a positionfacing the surface of the sensor chip on the casing.
 16. The analysisapparatus according to claim 1, wherein the light source generates alaser beam that excites Surface Plasmon Polariton, Localized SurfacePlasmon Resonance, and a Surface Enhanced Raman Scattering.